This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 7 |
| 3 | 91 |
| 4 | 679 |
| 5 | 5005 |
| 6 | 35287 |
| 7 | 248731 |
| 8 | 1742839 |
| 9 | 12211675 |
| 10 | 85493527 |
| 11 | 598537051 |
| 12 | 4189841719 |
| 13 | 29329466845 |
| 14 | 205306842727 |
| 15 | 1437151921051 |
| 16 | 10060067469319 |
| 17 | 70420500427165 |
| 18 | 492943531132087 |
| 19 | 3450604914906331 |
| 20 | 24154234601326039 |
| 21 | 169079643588071965 |